The present invention relates to a filter screen of the type employed in flow passages such as household plumbing systems for filtering particulate matter to prevent clogging and damage to appliances such as washing machines, dishwashers, ice-makers, and the like. Typically, filter screens are employed in such appliances at the inlet to the electrically operated inlet valve for preventing foreign particles in the plumbing and water supply from lodging in the valve and preventing closing of the valve.
Electrically operated appliance water inlet valves for the aforesaid types of appliances must, of necessity, provide very fine filtering of particles in order to prevent clogging and malfunction of the valve. Electrically operated appliance inlet valves typically employ pilot-operated mechanisms with very small diameter inlet passages which could be blocked by fine particulate matter in the water supply flowing through the valve. Furthermore, such valves typically employ rubber diaphragms as a movable valve member, which members are subject to erosion and tearing by foreign particles with sharp edges, such as silica sand and other crystalline materials encountered in typical household water supply systems.
Heretofore, filter screens for the aforesaid type appliance water inlet valves have been formed in a generally hat-shaped or domed configuration from screen materials having a fine mesh. Typically, the rim of the screen has been rolled to form an annular rib or reinforcement for mounting the screen in the valve inlet or flow passage. A common mounting technique has been to press-fit the rolled edge of the screen into the valve inlet. However, problems have been encountered in service with such dome-type inlet screens due to deformation of the screen during installation. The provision of the rolled edge for press fitting type installation of the screen in a bore necessarily reduces the diameter of the domed portion of the screen, and thus limits the amount of screen area available for filtering for a given passage size. Thus, it has been desired to provide for increased screen area for an inlet filter screen in a flow passage and yet provide for ease of installation and ready removal of the screen for field service.